The heating capability of an air source heat pump rapidly attenuates due to temperature reduction of an outdoor environment, and cannot meet user demands accordingly. A double-stage or quasi-double-stage compression intermediate air-supplying and enthalpy-enhancing technology, including two-stage throttling incomplete inter-cooling and one-stage throttling incomplete inter-cooling circulation, is adopted in the prior art, which may improve the low-temperature heating capacity and the COP, provides some help for reduction of the exhaust temperature of a compressor, and cannot meet actual application in cold regions. However, the prior art is limited in amplitude of improvement of the heating capacity and the COP, and is also limited in reduction of the exhaust temperature of the compressor. In addition, an air-supplying and enthalpy-enhancing proportion in the prior art is restricted by a displacement ratio of a high pressure stage to a low pressure stage, and application to a heat pump type air conditioner results in design incompatibility of capability and energy efficiency.